Klystron tubes



3 Sheets-Sheet 1 KLYSTRON TUBES SYSTEM ALONG A RIBBON BEAM INVENTOR. JOHANN R. HECHTEL FiG. l.

Jan. 26, 1965 Filed Jan. 20, 1960 WRMALIZED COORDINATE J. R. HECHTEL KLYSTRON TUBES Jan. 26, 1965 3 Sheets-Sheet 2 Filed Jan. 20. 1960 EDGE OF BEAM /l 0 l X .A D Em R w.\v. A N A MUE B 4\ MR R0 CA OOW CSAC 6 5 4 1 0 NORMALIZED DISTANCE ALONG BEAM,0'

FIG. 2.

INVENTOR. JOHANN R. HECHTEL Jan. 26, 1965 J. R. HECHTEL 3,167,684

KLYSTRON TUBES Filed Jan. 20, 1960 3 Sheets-Sheet 3 wpmw- FIG. 4.

B W1 9 FIG. 5.

ihj xvcj .42

' INVENTOR.

FIG. 6, JOHANN R. HECHTEL beam and V is the potential of the low voltage electrode. This expression may be found at page 259 of Vacuum Tubes, K. R. Spangenberg, published by McGraw-I-lill (30., New York, N.Y., 1948.' in accordance with well known mathematical techniques employing a Maclaurin or Taylor Series, if the potential V(x, y) in a two-dimensional coordinate system x, y is symmetrical about the plane of symmetry, V may be written where V0: V )y=0 6 V V0 6332 y=0 IV E V0 F0 The graphical representation of the relationship is shown in FIG. 1 and it is the exact solution for the equipotential lines adjacent a ribbon beam having rectilinear flow.

From the FIG. 1 plot it is possible to determine the potential, shape and spacing of electrodes necessary for rectilinear flow. This is because it has been found that an electrode may be substituted for a given equipotential line, having the same potential as the equipotential line and having the same spacing from the electron beam. The optimum spacing between adjacent electrodes for maximum current how can be determined from FIG. 1 since it can be determined analytically that the ratio V/ V of the above rectilinear fiow relationship must have an approximately 4/1 ratio in order to obtain maximum current flow. From FIG. 1 it can be seen that equipotential lines 1 and 4 fulfill this condition. Since equipotential lines 0, .25, .50 and .75 or any intermediate equipotential lines are equivalent to equipotential line 1 the ratio of V/V remains constant regardless of which is selected. Therefore, the longitudinal spacing from the symmetry plane of the zero potential electrode represented by the ==0 equipotential line, to the positive potential electrode, represented by the 6:4 equipotential line, is four units and the spacing from the beam edge to the zero potential electrode is approximately two units. The unit of length is given by the relation where x has the same meaning as formerly mentioned. Referring now to FIG. 2 of the drawings, there is shown a plot of the equipotential lines adjacent an axially symmetric beam having rectilinear flow derived by the numerical method disclosed in a publication entitled Electrostatic Potential Plotting for Use in Electron Optical Systems, by H. C. Ho and R. J. Moon, in the Journal of Applied Physics, vol. 24, pp. 1186l193, September 1953. The potentional distribution along the edge of the beam is the same as for the ribbon-beam of FIG. 1. To accurately determine the electric field or equipotential lines of a. finite axially symmetric beam it is necessary to employ a numerical method. Since the potential distribution along the edge of the beam is known, the electric field potential in the space surrounding the beam can be calculated from the relationship where a is the distance between adjacent points, r is the distance from the beam axis to the center point and V V V V and V are potentials one of which is unknown, all in accordance with well known mathematical techniques employed in deriving solutions by the numerical method. After determining the potential outside the beam, equipotential lines are constructed by graphical or numerical interpolation. In this manner the shape, potential and spacing of electrodes are determined in a similar way as for the ribbon-beam of FIG. 1.

In FIG. 3 is more clearly depicted the beam focusing electrode principle as determined from the analytical or numerical plot shown in FIGS. 1 and 2. An infinite number of possible electrode shapes could be employed to realize the field potential and configuration necessary for rectilinear electron beam flow. High potentional electrodes 12 and 14 consist of thin plates or disks having an opening for the electron beam. Low potential electrodes are denoted by equipotential lines 16, 18 and 20. In the case of a ribbon-beam the high voltage electrodes would have a thin slot somewhat larger than the beam and the low potential electrodes would comprise pairs of longitudinally extending cylinders the cross-sections thereof having the shape of the selected equipotential configuration. In the case of an axially symmetric beam the high voltage electrode would have a circular opening somewhat larger than the beam diameter and the low potential electrode would comprise the form of the surface of revolution generated by the selected equipotential configuration.

It is desirable that the selected electrode be spaced from the electron beam to prevent electron interception. Broken equipotential line 16 and solid equipotential line 29 represent the limits of the possible electrode spacing and configuration and broken equipotential line 18 represents a random selection of an electrode configuration between these limits. The selection of the particular electrode would depend to some extent upon the degree to which the tube may be overpowered thus resulting in beam expansion. Solid line 26 represents the electrode shape which is most desirable in a klystron since the equipotential line denoting the configuration thereof is at the same potential as the cathode. In addition, it is spaced suificiently from the beam so as to allow considerable beam expansion without electron interception.

The spacing of high potential electrodes 12 and 14 is denoted by the distance S and the spacing of the low potential electrode from the beam surface is denoted by the distance D. The proper spacing of the electrodes is determined from FIGS. 1 and 2. For maximum current density which can be focused by the system the relation D/SE25 exists for an electrode having cathode potential. This relation would increase with decrease in current density and decrease with the selection of an electrode closer to the beam surface.

It should be noted that an electrode could be used having the shape and potential of an equipotential line having a potential less than the cathode potential. However, an electrode of this type would not be practical because the system would require an additional negative voltage and the distance of the electrode from the beam would increase the size of the system.

The diagrammatic arrangements of FIGS. 4, 5 and 6 show a cathode 11, a beam focusing electrode 13 which is normally connected to the cathode, an input cavity resonator 15 and output cavity resonator 17 and a collector 19. Disposed between the input and output cavity resonators are electrodes for maintaining rectilinear beam characteristics.

In the FIG. 4 embodiment the beam focusing electrodes comprise high and low potential electrodes 21 and 23, respectively. The high potential electrode 21 comprises a thinplate or disk having an opening slightly larger than and of the same configuration as the electron beam. The shape, potential and spacing of the low potential electrode 23 is selected to conform with an equipotential line other than the zero or cathode equipotential lines of FIGS. 1 or 2. The transverse wall of cavity resonators 15 and 17 nearest a low potential electrode 23 and the disk electrodes 21 correspond to the high potential electrodes 12 and 14 shown in FIG. 3. It should be recognized that in the case of a ribbon-beam the low potential electrodes would comprise longitudinally extended cylinders whereas in the case of a circular or axially symmetric beam the low potential electrodes would comprise the surface of a cavity or open space within the electrode. In this em bodiment it is necessary that the electron tube have a minimum of three different potentials.

The embodiments of FIGS. 5 and 6 employ low poten: tial electrodes that have the same potential as the cathode. In FIG. 5 is shown a single electrode 25 having the cathode potential wherein the input and output resonators function as the high potential electrodes as well as cavity resonators, the transverse walls of cavity resonators 15 and 17 nearest low potential electrode 25 corresponding to the high potential electrodes 12 and 14 shown in FIG. 3. FIG. 6 illustrates a tube having a relatively long drift space wherein it'is necessary to employ a greater number of focusing electrodes. In both of these embodiments the shape and spacing of the low potential electrode is determined from the zero or cathode potential equipotential lines of FIGS. 1 or 2.

Obviously many modifications and variations of the,

present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is: t

1. The improvements for use with a velocity modulated electron tube having a cathode forming a circular cross sectioned electron beam for flow along a longitudinal axis, an input cavity resonator, and an output cavity resonator, comprising; a

(a) electrode means for maintaining rectilinear electron beam flow along the length otsaid beam between the input and output cavity resonators, said electrode means including a set of first, second and third elements longitudinally spaced along said beam with the second element interposed between the first and third elements,

(b) said first element being formed from a transverse wall of the input cavity resonator forming a wall face in axially confronting relationship to said second element, said transverse wall of the input cavity resonator having a central aperture through which the beam emerges from the input cavity resonator,

(c) said second element being a concentrically aligned toroidal member forming a radially inwardly facing surface of revolution defined by the revolution of a radially inwardly convex curve which is bi-laterally symmetrical about a transverse reference plane and having one of its bi-lateral halves shaped and spaced from the edge of the beam in accordance with the curve =0, as shown in FIG. 2,

(d) said third element being formed from a transverse wall of the output cavity resonator forming a wall face in axially confronting relationship to the second element, said transverse wall of the output cavity resonator having a central aperture through which the beam enters the output cavity resonator,

(e) said transverse walls of the input and output cavity resonators being equi-distantly spaced from said reference plane and spaced apart from one another by an axial distance which is approximately four times the radial distance from the edge of the beam to the nearest portion of said radially inwardly convex curve,

(1) means for applying a potential equal to the cathode potential to said second element, and

(g) means for applying a predetermined potential more 6 positive than said cathode potential to said first and third elements.

2. The improvements for use with a velocity modulated electron tube having a cathode forming a ribbon flow electron beam which flows along a longitudinal axis, an input cavity resonator, and an output cavity resonator, comprising;

(a) electrode means for maintaining rectilinear electron beam flow along the length of said beam between the input and output cavity resonators, said electrode means including a set of first, second and third elements longitudinally spaced along said beam with the second element interposed between the first and third elements,

(b) said first element being formed from a transverse wall of the input cavity resonator forming a wall face in axially confronting relationship to said second element, said transverse wall of the input cavity resonator having a central aperture through which the beam emerges from the input cavity resonator,

(c) said second element comprising a pair of curved members disposed in opposed relationship across the thickness dimension of the ribbon beam, said curved members each forming a curved surface extending linearly in the direction of thickness of the ribbon beam and of uniform curvature along its linear expanse, said uniform curvature being defined by a curve which is convex in the direction of the beam and which is bi-lat'erally symmetrical abouta transverse reference plane and having one of the bilateral halves of the curve shaped and spaced from the edge of the beam in accordance with the curve =0, as shown in FIG. 1, r

(d) said third element being formed from a transverse wall of the output cavity resonator forming a wall face in axially confronting relationship to the second element, said transverse wall of the output cavity resonator having a central aperture through which the beam enters the output cavity resonator,

(e) said transverse walls of the input and output cavity resonators being equi-distantly spaced from said reference plane and spaced apart from one another by an axial distance Which is approximately four times the radial distance from the edge of the beam to the nearest portion of said radially inwardly convex curve,

(f) means for applying a potential equal to the cathode potential to said second element, and

(g) means for applying a predetermined potential more positive than said cathode potential to said first and third elements.-

References Cited by the Examiner UNITED STATES PATENTS GEORGE N. WESTBY, Primary Examiner.

ARTHUR GAUSS, RALPH G. NILSON, Examiners. 

1. THE IMPROVEMENTS FOR USE WITH A VELOCITY MODULATED ELECTRON TUBE HAVING A CATHODE FORMING A CIRCULAR CROSS SECTIONED ELECTRON BEAM FOR FLOW ALONG A LONGITUDINAL AXIS, AN INPUT CAVITY RESONATOR, AND AN OUTPUT CAVITY RESONATOR, COMPRISING; (A) ELECTRODE MEANS FOR MAINTAINING RECTILINEAR ELECTRON BEAM FLOW ALONG THE LENGTH OF SAID BEAM BETWEEN THE INPUT AND OUTPUT CAVITY RESONATORS, SAID ELECTRODE MEANS INCLUDING A SET OF FIRST, SECOND AND THIRD ELEMENTS LONGITUDINALLY SPACED ALONG SAID BEAM WITH THE SECOND ELEMENT INTERPOSED BETWEEN THE FIRST AND THIRD ELEMENTS, (B) SAID FIRST ELEMENT BEING FORMED FROM A TRANSVERSE WALL OF THE INPUT CAVITY RESONATOR FORMING A WALL FACE IN AXIALLY CONFRONTING RELATIONSHIP TO SAID SECOND ELEMENT, SAID TRANSVERSE WALL OF THE INPUT CAVITY RESONATOR HAVING A CENTRAL APERTURE THROUGH WHICH THE BEAM EMERGES FROM THE INPUT CAVITY RESONATOR, (C) SAID SECOND ELEMENT BEING A CONCENTRICALLY ALIGNED TOROIDAL MEMBER FORMING A RADIALLY INWARDLY FACING SURFACE OF REVOLUTION DEFINED BY THE REVOLUTION OF A RADIALLY INWARDLY CONVEX CURVE WHICH IS BI-LATERALLY SYMMETRICAL ABOUT A TRANSVERSE REFERENCE PLANE AND HAVING ONE OF ITS BI-LATERAL HALVES SHAPED AND SPACED FROM THE EDGE OF THE BEAM IN ACCORDANCE WITH THE CURVE $=0, AS SHOWN IN FIG. 2, (D) SAID THIRD ELEMENT BEING FORMED FROM A TRANSVERSE WALL OF THE OUTPUT CAVITY RESONATOR FORMING A WALL FACE IN AXIALLY CONFRONTING RELATIONSHIP TO THE SECOND ELEMENT, SAID TRANSVERSE WALL OF THE OUTPUT CAVITY RESONATOR HAVING A CENTRAL APERTURE THROUGH WHICH THE BEAM ENTERS THE OUTPUT CAVITY RESONATOR, (E) SAID TRANSVERSE WALLS OF THE INPUT AND OUTPUT CAVITY RESONATORS BEING EQUI-DISTANTLY SPACED FROM SAID REFERENCE PLANE AND SPACED APART FROM ONE ANOTHER BY AN AXIAL DISTANCE WHICH IS APPROXIMATELY FOUR TIMES THE RADIAL DISTANCE FROM THE EDGE OF THE BEAM TO THE NEAREST PORTION OF SAID RADIALLY INWARDLY CONVEX CURVE, (F) MEANS FOR APPLYING A POTENTIAL EQUAL TO THE CATHODE POTENTIAL TO SAID SECOND ELEMENT, AND (G) MEANS FOR APPLYING A PREDETERMINED POTENTIAL MORE POSITIVE THAN SAID CATHODE POTENTIAL TO SAID FIRST AND THIRD ELEMENTS. 